Are AMD manuscripts a-theoretical?

Absolutely not. Theory is critically important for any advancement of knowledge, but our appreciation of the roles of theory in scholarship needs to broaden. All data-driven explorations are theory-laden to some extent; one cannot consider evidence in a meaningful way without engaging in "sensemaking." AMD papers very much rely on theory, but it is theory in service of describing, understanding, and narrowing the range of plausible explanations for phenomena and relationships, rather than theory in service of testing and confirmation as has been the case in AMJ and other empirical journals in the field of management.